Disability glare reduction following surgery in patients with dense cataracts: Differences between self-report and two psychophysical measures

Purpose. All existing disability glare testers that are based on psychophysical methods have one or more design faults, such as no control of light adaptation, or pupil size. We have developed a new disability glare instrument that addresses these design issues. The present study is an initial test of the validity of this instrument on one group of patients with certain characteristics. Methods. Disability glare was assessed in 36 patients before and after cataract removal. All had advanced cataracts with a mean Snellen acuity of 20/71. Three instruments were used: 1. Glare disability score from the "Activities of Daily Vision Scale" (ADVS); 2. The Pelli-Robson contrast sensitivity chart with and without glare from the "Brightness Acuity Tester" (PR/BAT); 3. A new Prototype instrument which is based on detecting a small flashing test on a light-adapting background, with and without a glare surround; all stimuli were restricted by a small artificial pupil. Results. The ADVS glare score was highly significantly better after surgery than before. The PR/BAT and the Prototype measurements showed a slight (insignificant) trend toward improvement following surgery. No correlation was found between the improvement in the ADVS score, and the improvements in the PR/BAT and Prototype scores. Conclusions. Psychophysical glare testing may be of little use in making a decision on the advisability of cataract surgery in patients with dense, advanced cataracts. In such patients, the cataract may restrict the effect of a glare source: the opacity does not allow enough forward scatter to raise thresholds for detection or contrast. Most of the glare source is either absorbed by the opacity or scattered backwards. Psychophysical glare testing may be much more useful in patients with early cataracts but whose everyday visual function is impaired by glare.